loading tokens indicator

[owocki]

Description

im tired of answering questions from people about why DAI, or other tokens, arent showing up in their token dropdowns
here is a mock of a simple indicator that the token list is drawn from your web3 wallet. it can probably be improved

Refers/Fixes

https://gitcoincore.slack.com/archives/CAW05FUD7/p1589892852270300

Testing

tested locally

[codecov]

Codecov Report

Merging #6681 into master will decrease coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #6681      +/-   ##
==========================================
- Coverage   27.13%   27.09%   -0.05%     
==========================================
  Files         291      291              
  Lines       27050    27039      -11     
  Branches     3982     3983       +1     
==========================================
- Hits         7339     7325      -14     
+ Misses      19443    19442       -1     
- Partials      268      272       +4     

Impacted Files	Coverage Δ
app/dashboard/embed.py	28.16% <0.00%> (-3.45%)	⬇️
app/dashboard/router.py	40.48% <0.00%> (-0.41%)	⬇️
app/dashboard/admin.py	57.96% <0.00%> (-0.12%)	⬇️
app/dashboard/models.py	50.35% <0.00%> (-0.10%)	⬇️
app/dashboard/helpers.py	14.19% <0.00%> (-0.07%)	⬇️
app/retail/emails.py	22.41% <0.00%> (-0.04%)	⬇️
...rketing/management/commands/no_applicants_email.py	0.00% <0.00%> (ø)
...eting/management/commands/assemble_leaderboards.py	40.05% <0.00%> (ø)
app/dashboard/views.py	11.04% <0.00%> (+0.02%)	⬆️

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